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Surveillance for Epidemics -- United States

MMWR 38(40);694-696

Publication date: 10/13/1989

Table of Contents

Article

Although state health departments document investigations of disease
epidemics and outbreaks, there is no national system for surveillance of
epidemics. In 1988, a 5-month pilot project to assess the feasibility and
utility of a standard computerized surveillance system for epidemics was
conducted by state epidemiology programs in Maryland, New York, Oklahoma,
and Washington, and by the Epidemiology Program Office, CDC.

From June through October, 1988, the four participating state
epidemiology offices used a uniform data collection system to record
reported epidemics investigated by their staffs or by other agencies in
their states. For this project, an epidemic or outbreak was defined as: "A
recent or sudden excess of cases of a specific disease or clinical
syndrome. For a foodborne outbreak, ngreater than or equal to 2; for other
outbreaks, n greater than or equal to 3." Although designed principally to
collect information on epidemics, the system also allowed for reporting
other epidemiologically important events, including individual cases of
rare diseases (e.g., botulism and human rabies) and toxic exposures without
documented subsequent illness (e.g., a hazardous material spill during
transport).

During the 5 months, 116 events were reported. Maryland and Oklahoma,
which already maintained systems of epidemic reporting similar to the pilot
system, accounted for 39 (34%) and 33 (28%) reports, respectively.
Washington and New York, with pre-existing systems considerably different
from the pilot system, accounted for 25 (22%) and 19 (16%), respectively.
The number of reported events per 100,000 population was 1.0 in Oklahoma,
0.8 in Maryland, 0.5 in Washington, and 0.1 in New York (1). Local
health departments originated reports for 69 (59%) events. The timeliness
of reporting was measured as the interval between date of onset for the
index case and date of report to the state health department. Dates were
recorded for 106 events; of these, the reporting interval was less than or
equal to 1 week for 64 (60%) and less than or equal to 2 weeks for 78
(74%).

Seventy-nine (68%) of the events were epidemics or outbreaks; of these,
77 (97%) were caused by communicable diseases. The majority of these were
relatively small outbreaks--51 (66%) involved less than 10 persons. The
largest, an outbreak of viral gastroenteritis, involved 64 persons at a
nursing home in Oklahoma. The most frequently reported locations associated
with outbreaks were commercial food establishments (25%), nursing
homes or other long-term care facilities (15%), and the general community
(10%). For the 39 (51%) infectious disease outbreaks in which an etiologic
agent was reported, the most common agents were Salmonella (26%) and
hepatitis A virus (23%).

Reported by: C Groves, E Israel, MD, State Epidemiologist, Maryland State
Dept of Health and Mental Hygiene. S Kondracki, DL Morse, MD, State
Epidemiologist, New York State Dept of Health. P Archer, S McNabb, GR
Istre, MD, State Epidemiologist, Oklahoma State Dept of Health. M Chadden,
JM Kobayashi, MD, State Epidemiologist, Washington State Dept of Social and
Health Svcs. Council of State and Territorial Epidemiologists. Div of Field
Svcs, Epidemiology Program Office, CDC.

Editorial Note

Editorial Note: The current national system of notifiable disease reporting
(data reported weekly in MMWR Tables I, II, and III (pages 688-691))
provides surveillance data on a wide range of diseases, many of which can
cause epidemics. The 121-city mortality surveillance system (data reported
weekly in MMWR Table IV (page 692)) is used to assist in identifying
epidemic influenza (2). However, except for a limited set of problems
(e.g., waterborne outbreaks (3)), no uniform national system of
surveillance exists for epidemics. Consequently, neither CDC nor
state epidemiology programs have access to uniform, comparable surveillance
data for monitoring temporal and geographic trends of epidemics or for
providing national estimates of the frequency of epidemics.

Although most states maintain written records for epidemic surveillance,
many do not routinely computerize these data. Increased use of automation
might facilitate analysis and evaluation of such data, as well as expedite
intervention/prevention efforts. Systematic surveillance of epidemics could
be used to improve disease prevention efforts at both state and national
levels. For example, epidemic surveillance data could be used to evaluate
and improve regulations and standards of public health practice related to
child-care licensing, restaurant inspections, and environmental hazard
control. This approach might permit comparison of the effectiveness of
differing standards in different local or state jurisdictions, measurement
of the impact of changes in standards over time, and early detection of
changing patterns in the transmission of notifiable diseases, such as the
recent increased incidence of hepatitis A transmission among drug abusers
(4).

This pilot project demonstrated both the feasibility and constraints
associated with development of a standard system for surveillance of
epidemics. Each of the par ticipating states recognized the utility of the
data generated by the project. However, two of the states noted that a
permanent system would require substantial revision of their current
procedures for collecting and reporting surveillance data. The wide
variability of the ratio of reported events to population size probably
reflects differences in data included in this system rather than in
occurrence of epidemics (e.g., most reports of small foodborne disease
outbreaks in New York come directly to the State Bureau of Community
Sanitation and Food Protection rather than to the office of the state
epidemiologist).

At its annual meeting in May 1989, the Council of State and Territorial
Epidemiologists unanimously passed a resolution supportingthe concept of
state-based epidemic surveillance and endorsed CDC efforts to develop a
uniform system that permits comparable information to be collected,
analyzed, and shared among the states.

References

Bureau of the Census. Annual estimates of the resident population of
states: April 1, 1980 to July 1, 1988. Washington, DC: US Department of
Commerce, Bureau of the Census, 1989; release no. CB89-47.

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